I can't read what size the main breaker is. It should be a 100 amp but the important thing is that it is fed by at least a #2 gauge copper wire. It has to be at least that size to carry 100 amps. Main breaker is supposed to be sized to trip before the wire burns up. #2 copper is good to carry 100 amps thus can have a 100 amp breaker. I have seen where somebody has put a 100 amp breaker on smaller wire, that does not make it a 100 amp service. Wire could burn up before breaker trips.
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